It is well know that pressure operated switch constructions have been provided wherein each has a base carrying a pressure operated diaphragm. Such switches typically include an electrical switch unit controlled by the diaphragm and an adjustable compression spring that, in turn, is controlled by a cam operated actuator leaf pivotally carried by the base. Such pressure switches are often used to control the water level in consumer and commercial appliances, for example, clothes washing machines.
General operation of a pressure switch construction for controlling the liquid level in a washing machine is well known in the art. Briefly, a user selects a desired water level by rotating an external knob which is connected to a cam. This cam may have a continuously varying cam surface or discrete lobes thereon that define discrete water levels. The cam at the user selected position preloads the calibration spring of the pressure switch. As the water within the washing machine rises, the pressure from the height of the water lifts the diaphragm in the pressure switch until the force of the spring equals the height of the water. Once this occurs, the electrical switch within the pressure switch typically actuates to begin the next cycle, for example, the drain cycle. Such constructions and operations are well known as set forth in, for example, U.S. Pat. No. 4,081,637 to Stearley et al., U.S. Pat. No. 3,249,712 to Rhodes et al., and U.S. Pat. No. 5,336,858 to Kaigler, the teachings and disclosure of which are hereby incorporated in their entireties by reference thereto.
While the construction and operation of such pressure switches allow for the reliable automatic control of water levels during the various cycles of the programmed operation of the washing machine, embodiments of the present invention are directed to improvements on such pressure switches that allow for energy saving operation.
These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.